This application is based on application No. Hei 11-275380 filed in Japanese Industrial Property Office on Sep. 28, 1999, the content of which is incorporated hereinto by reference.
(a) Field of the Invention
This invention relates to an anode and an electrode for a lithium secondary battery, a lithium secondary battery, and a method for preparing an anode, and, more particularly, the present invention relates to the material of an anode, which is a metal compound coated on a carbon material.
(b) Description of the Related Art
With the proliferation of portable electronics devices in recent times, coupled with advancements which have enhances performance and enabled increasingly smaller sizes and weights for these devices, research is being actively pursued to improve the energy density of secondary batteries.
However, though graphite, one of the anode active materials traditionally used in secondary batteries, has a theoretical capacity of 372 mAh/g, in order to achieve higher capacity, multi-materials need to be developed which are quite different from graphite or materials which have graphite as the main component.
For some time tin compounds have been examined for use as anode active materials in place of graphites. It is common knowledge that the tin of in these tin compounds can form an alloy with lithium and has greater capacity than graphite.
But, as compared with graphite, these tin compounds have low initial charge capacity, a non-plain discharge curve, and bad charge-discharge properties. Accordingly, tin compounds are not widely used as anode active materials at the present time.
In spite of these defects, tin compounds are regarded as a promising anode active material because the tin compounds have much greater charge-discharge capacity than graphite.
It is an object of the present invention to provide an anode material capable of serving as an anode active material having an excellent charge-discharge cycle, a flat discharge curve, a high charge-discharge efficiency, and a great charge-discharge capacity.
It is another object to provide a method for preparing an anode material, an electrode and a lithium secondary battery having the anode material.